Classes: Agnatha, Chondrichthyes, and Osteichthyes FISHIES Classes: Agnatha, Chondrichthyes, and Osteichthyes

Fish are the dominant aquatic vertebrates.

Fish have adaptations to an aquatic environment that make their movements through water energy-efficient.

Arapaima South American Freshwater Fish

Internal Anatomy of Bony Fish

Gills Large sheets of thin frilly tissue filled with capillaries that take in dissolved oxygen from the water and release carbon dioxide.

Circulatory system: pumps blood in a single loop through a two chambered heart.

Countercurrent Flow The opposite movement of water against the flow of blood in the fish’s gills. Maximizes the amount of oxygen the fish can pull from the water.

Swimming and Maneuvering Most fish swim by contracting large segmented muscles on either side of their body from the head to the tail. This makes an S-shaped wave that pushes it through the water. They counteract these movements with their fins.

External Anatomy of Bony Fish

Fins Surfaces that project from a fish’s body Keep the fish stable Direct the movement of the fish

Fins

Jawless Fish Class Agnatha Existed since the Cambrian and continues to live Do not have paired fins Have a notochord in both larvae and adults Light sensitive pineal eye No identifiable stomach Ectothermic Two-chambered heart External Fertilization

Sea Lamprey Petromyzon marinus

Hagfish Myxine glutinosa

Jaws Evolved from gill arches Most jawed vertebrates have teeth on their upper and lower jaws. Teeth used to capture and process food

Jaws Gave vertebrates a huge advantage as predators and pushed them to the top of the food chain.

Two groups of jawed fish still exist: Cartilaginous Fish and Bony fish

Cartilaginous Fish Skeletons made of cartilage while ancestors had skeletons made of bone They have lost the ability to make bone Cartilage is unique – it’s stronger than human cartilage.

Two Groups of Cartilaginous Fish Holocephali: chimeras Elasmobrachs: sharks, rays and skates

Holocephali: chimeras Small group of deep-sea fish with platelike grinding teeth. Feed on crustaceans and other invertebrates

Elasmobranchs: sharks, rays and skates 300 species of sharks 400 species of rays and skates Ray Skate

Sharks Most hunt other fish Some eat seals and sea lions

Filter feeder, eats plankton Biggest Sharks Whale Sharks Feed on plankton, krill and algae Basking Sharks Filter feeder, eats plankton

Great White Shark

All Fish Have a lateral line system This is a series of shallow canals on the sides of the fish made up of cells that are sensitive to small changes in water movement. This allows them to have a sense of “distant touch”.

External Anatomy of Bony Fish

Class Osteichthyes Bony Fish More than 20,000 species Living in nearly every aquatic environment on Earth Some have become parasites of other fish One group can even spend short periods of time on land

Characteristics internal skeleton ossified (i.e., endochondral bone) swim bladder or lung present bony scales (ganoid, cycloid, ctenoid, or cosmoid) gill slits covered by an operculum (single external gill opening) late Silurian to Recent

Seahorse Genus Hippocampus Unique because males become pregnant when the females deposit the eggs into the birthing pouch.

Nile Knifefish Will aggressively bite anything that moves Discharges an electrical charge